Driven by direct and indirect legislations, electrification will be required for compliance in the future automotive world. For hybrid and electric vehicles, heat pump systems represent a proven solution to extend the driving range of electrified vehicles and hold significant potential in meeting the increasing demands on electrification. Compared to heating methods using high voltage positive temperature coefficient (HV-PTC) heaters or phase-change material (PCM) heat storage, for example, a heat pump system may extend the driving range by up to 30% (FTP drive cycle at −10° C.; supplier data).
Since technological advances allow many electrified vehicles to routinely travel over 200 miles without recharging, the improvement to the driving range afforded these vehicles through utilization of heat pump systems may not, alone, be sufficient to justify the use of these systems. This is particularly true given the fact that most electrified vehicles with heat pump systems are also equipped with HV-PTC heaters as a supplemental heating source in low ambient conditions (e.g., an ambient temperature below approximately a minus seven degrees Celsius (−7° C.). When combined with the required valves, controls, and expansion device(s) required to make the system operate, the overall cost of heat pump systems is greater than desired.
For plug-in hybrid electric vehicles where engine heating is available, some organizations have attempted to eliminate the need for HV-PTC heaters and the like in low ambient conditions utilizing a vapor injection heat pump. However, the vapor injection feature or mode of operation is only activated in a heating mode of operation. In order to overcome these issues, a need exists for such a vapor injection heat pump system that is capable of activation in more modes of operation than just a heating mode (e.g., a cooling mode of operation). Such a design would take full benefits of vapor injection and address degradation performance issues in both high and low ambient conditions, making it a more competitive solution for use in vehicle climate control and thermal management.